Heavy-ion fusion-evaporation reactions: high spin states inCa43andSc43

Fusion-evaporation reactions, primarily ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({}_{}{}^{19}{}_{}{}^{}\mathrm{F},n2p){}_{}{}^{43}{}_{}{}^{}\mathrm{Ca}$ and ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}({}_{}{}^{19}{}_{}{}^{}\mathrm{F},2np){}_{}{}^{43}{}_{}{}^{}\mathrm{Sc}$, have been used to investigate the structure and formation of the residual nuclei. Decay schemes of the yrast levels which are populated are presented together with suggested spin assignments for some of the higher levels. Incidental results obtained for the nuclei ${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{44}{}_{}{}^{}\mathrm{Sc}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ are also discussed. Mean lifetimes measured by the recoil distance method are as follows: (${}_{}{}^{43}{}_{}{}^{}\mathrm{Ca}$): 2754-keV level, $\tau =34.1\mathrm{}\pm 1.5$ psec; 990-keV level, $\tau =73\mathrm{}\pm 11$ psec; (${}_{}{}^{43}{}_{}{}^{}\mathrm{Sc}$): 880-keV level, $\tau =7.0\mathrm{}\pm 1.4$ psec; 472-keV level, $\tau =233\mathrm{}\pm 53$ psec; (${}_{}{}^{44}{}_{}{}^{}\mathrm{Ca}$): 3285-keV level, $\tau =23\mathrm{}\pm 7$ psec, 2283-keV level, $\tau <25\mathrm{}$ psec; (${}_{}{}^{44}{}_{}{}^{}\mathrm{Sc}$): 631-keV level, $\tau =550\mathrm{}\pm 80$ psec; 3567-keV level, $\tau =51\mathrm{}\pm 10$ psec. The properties of the high spin states populated in the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ + ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$ fusion-evaporation reaction are discussed. Relative excitation intensities of the residual nuclei are interpreted in terms of a Hauser-Feshbach calculation, while a simplified pairing force model allows us to explain a number of observations in specific nuclei. NUCLEAR REACTIONS